1. Field of the Invention
The present invention relates to an automatic speed-change apparatus for a gear transmission.
2. Description of the Prior Art
In the prior art, there is a speed-change apparatus in which the mechanism for the manual gear transmission is used as it is and the speed change and the clutch operation are automated through the hydraulic apparatus by the computer control. However, it requires three cylinders for clutch, shift and select, and a number of electromagnetic valves to actuate those cylinders and further requires a hydraulic system, so that it has such problems as complicated structure, large size and high cost.
Also, a speed-change apparatus in which motors are used as actuators to select or shift the gear transmission has been disclosed in JP publication Toku-ko-sho 61-51697, for example. However, in this apparatus the respective motors are used for the select and the shift mechanism, and a plurality of solenoids are used for the select mechanism. That is, this apparatus requires certain numbers of motors depending on the numbers of the select lines, and because of using a plurality of motors or solenoids, it results in a complicated structure and large size apparatus and further in high cost.